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Thursday, July 25, 2019

Dengue fever Transmission, Symptoms, Treatment



Dengue is a self-limiting acute mosquito transmitted disease characterized by fever, headache, muscle, joint pains, rash, nausea and vomiting. Dengue Fever (DF) is caused by an arbovirus and spread by Aedes mosquitoes. Some infections result in Dengue Haemorrhagic Fever (DHF) and in its severe form Dengue Shock Syndrome (DSS) can threaten the patientís life primarily through increased vascular permeability and shock.

Incubation Period

It means the time between bite of an infected mosquito and appearance of symptoms of dengue fever in the bitten person. Commonly, it is 5-6 days. However it can vary from 3-10 days.


It is known that dengue fever is caused by the bite of female Aedes mosquito commonly known as A. aegypti. It is found that these types of mosquitoes live in the area of 35 degree from south and 35 degree north from the latitude which is below in the angle of elevation 1000 metres (3,300 ft). Aedes mosquitoes mainly attack during the morning time and evening time.
Aedes is the mosquitoes that have its many species transmitting disease are A.scutellaris, A.albopictusand last but not least is A.polynesiensis. Humans are known for the host of virus but it is found that virus also circulates in the primates of non-human. The infection from Aedes can be transmitted on a single bite.
It is stated that female Aedes also get infected while sucking the blood of a person who is infected with dengue fever. Dengue is the fever which is also transmitted through the blood products which is infected and also through the donation of an organ.

Types of dengue fever

There are several types of dengue fever which affect one’s life and may lead to fatal conditions. They are as follows:
  1. Classical (Simple) Dengue Fever
  2. Dengue Haemorrhagic Fever (DHF)
  3. Dengue Shock Syndrome (DSS)


The disease of Dengue was first reported in China during the 265 – 420 CE. But according to the American Society for Microbiology, a dengue-like disease was first detected in 1779 at Jakarta and Cairo, though the transmission by Aegypti was not confirmed before 1906.
Another fascinating account of the origin of Dengue takes us to Africa, where it was spread worldwide via slave trade. The name dengue is derived from the Swahili “Ka-Dinga Pepo” which means “cramp like disease caused by an evil spirit”.


  • Before 1970, only nine countries had experienced severe dengue epidemics. Now, the disease is widespread (endemic) in more than 100 countries worldwide.
  • About half of the world’s population is at risk for dengue infection.
  • An estimated 500,000 people with severe dengue require hospitalization each year. The mortality rate in this group is about 2.5 percent.
  • The island of Hawaii (the “Big Island”) was affected by an outbreak of dengue from September 2015 to March 2016, during which 264 cases were reported.

What Causes Dengue Fever?

  • The viruses that cause dengue fever are spread by mosquitoes of the species Aedes aegypti, and sometimes also by Aedes albopictus.

Aedes aegypti

Aedes albopictus

  • The viruses jumped from monkeys to humans between 100 and 800 years ago, according to the CDC, but dengue remained a minor problem until the middle of the twentieth century.
  • Aedes mosquitoes are usually found in urban and suburban areas, as they like to breed in man-made containers like tires, flowerpots, and household water.
  • Aedes albopictus mosquitos have been transported to North America and Europe by Asian products like used tires and lucky bamboo.
  • These mosquitos can survive subfreezing temperatures, which has allowed dengue to spread to cooler climates.

Breeding areas of dengue mosquitos

What Are Dengue Fever Risk Factors?

The risk factors for dengue fever are as follows:
  • Traveling to or living in endemic or outbreak areas, especially if no mosquito control is attempted by the people or government
  • Mosquito bites
  • A repeated infection with another serovar of dengue virus with antibodies in the serum active against the first infecting virus type
  • Not taking precautions to avoid mosquito bites


Dengue Fever
The symptoms of dengue fever are less in appearance in the case of children who are in young stage and for grown up children and adults, these symptoms start appearing. They are as follows:
  • Fever which is sudden in onset and remain for last 3-7 days of time period.
  • Severe headache especially in the back portion of the eyes.
  • Pain in the muscles and joints of a victim especially in ankle and elbow.
  • Taste of the mouth getting changed.
  • One can prone to vomiting, abdominal pain accompanied by loss in one’s appetite.
  • Skin rashes, itching on the skin, legs etc.
  • There is minor bleeding from the part of body like from nose, gums etc which is accompanied with heavy periods of menstrual.
  • Skin from the neck and face start getting flushed.
  • Person feels tiredness.
Dengue Hemorrhagic Fever (DHF)
DHF is one of the complicated diseases which can turn fatal. DHF is the fever which occurs only when the person is prone to dengue for more than one time. DHF is very similar to the symptoms of dengue fever. DHF is the fever which is very critical in nature than dengue fever. The symptoms for DHF are as follows:
  • After the fever, for 2-5 days the symptoms start appearing, but the symptoms start decreasing when the fever starts resolving.
  • The health of the patient decreases after the few days of the fever and there is minor bleeding from nose, gums, skin etc which make the bruises purplish in color.
  • In some cases it is found that after resolving of the fever, there is failure in the functioning of the circulatory system caused which turns into shock and leads to death of the patient within 12 to 24 hours.
Dengue Shock Syndrome
If the person is aware about the signs and symptoms of dengue than the patient can survive by taking proper medical treatment. DSS is one of the severe situations of a dengue which can lead the patient to get hospitalized, in case the following symptoms are found. They are as follows:
  • Pain in abdominal part f the body
  • Vomiting accompanied by the flow of minor blood
  • Body temperature star getting fluctuated
  • Blood pressure of the body getting low
  • Irritation in the nature
If there is an appearance of any of these symptoms, one can get to take the medical treatment as soon as possible because DSS is the fever which can lead to death within the time period of 24 hours

What are the Complications of Dengue Fever?

Dengue fever may sometimes develop into more dangerous forms such as dengue hemorrhagic fever or dengue shock syndrome, which may lead to the development of life-threatening symptoms. Some of the complications caused by the disease include:
  • Severe dehydration
  • Continuous bleeding
  • Low platelets, due to which clotting of blood doesn’t occur
  • Blood pressure may go dangerously low
  • Bradycardia (heart beating less than 60 counts per minute)
  • Damage to the brain due to bleeding, seizures or encephalitis
  • Damage to the immune system
  • Enlargement of liver and liver damage

How Do You Diagnose Dengue Fever?

Diagnosis of dengue is considered when sudden high fever is accompanied by severe body, muscle or joint pain. It is important to be evaluated when a person develops fever within two weeks of being in the tropics or sub-tropics. Dengue often causes symptoms that are similar to other diseases such as flu, measles, and typhoid fever etc. Hence investigations are always performed to exclude other disease conditions. Usually, the blood of the patient is tested for the presence of antibodies and virus. Diagnosis of dengue infection can be done by the following methods:
  • Isolating the virus by collecting serum sample from patients within 5 days of appearance of symptoms.
  • Detection of specific antibodies can be done by collecting serum within 6 days after onset of symptoms. The serum is tested for specific anti-dengue antibodies by Enzyme-linked Immunosorbent Assay (ELISA). Titres of IgM and IgG antibodies increase four-fold in serum sample.
  • Using Polymerase Chain Reaction (PCR) for detecting viral genomic sequence from Serum or Cerebro Spinal Fluid (CSF) samples collected from the patient, which is more expensive and complicated.
  • In the case of more serious complications such as dengue hemorrhagic fever, the following diagnosis must be performed:
  • A tourniquet test is to be conducted, where a tourniquet is tied to the arm and if blood blotches tend to appear beyond the tourniquet, the patient may be suffering from increased bleeding, which may indicate dengue hemorrhagic fever
  • A decrease in platelet count, also known as thrombocytopenia occurs when platelet count falls below 100,000. Normal platelet counts are between 150,000 to 400,000. A decreased platelet count may be due to dengue fever.
  • An increase in hematocrit i.e., the volume percentage of red blood cells (RBCs), by 20% could be another indicator as it occurs due to a rise in the vascular permeability of the plasma. Signs of plasma leakage appear as increased fluid accumulation in the chest and abdominal cavity known as pleural effusion or ascites respectively.

How Do You Treat Dengue Fever?

  • Since there are no known antiviral drugs or injections available for the cure of the disease, dengue fever treatment or management mainly involves plenty of supportive care that would eventually help save the patient’s life.
  • Dengue is characterized by fever and intense body ache. Dengue treatment comprises of reducing the fever with antipyretic drugs such as paracetamol and the body ache with analgesics that help relieve the pain.
  • Drugs such as aspirin and ibuprofen should be avoided as they may increase the risk of hemorrhage.
  • The patient can also be treated with natural home remedies such as papaya leaves, kiwi and other food items that have been proven to help in the increase of platelet count, which becomes lower during dengue.
  • In the case of more severe forms of dengue, such as dengue hemorrhagic disease or dengue shock syndrome, the patient must be admitted to a hospital immediately and given proper care.
  • Treatments such as intravenous fluid replacement should be administered to these patients to prevent shock. Patients should drink plenty of fluids, as dehydration is common among those affected with Dengue.

Dengue Vaccine

  • The world’s first dengue vaccine, Dengvaxia or CYD-TDV) developed by Sanofi Pasteur was approved for use in Mexico, Philippines and Brazil in December 2015 for the prevention of the deadly mosquito borne disease in people living in dengue endemic areas.
  • New dengue vaccines TV003/TV005 have been developed by the National Institute of Allergy and Infectious Diseases. They produce antibodies to all 4 dengue virus serotypes. In earlier trials, a single dose of either of the vaccines was able to elicit a robust antibody and cellular immune response.
  • Another vaccine developed by Takeda called the Tetravalent Dengue Vaccine (TDV) has also entered its Phase 3 trials early in 2016 in Latin America and Asia.

How to Prevent Dengue Fever

There is no vaccine to prevent dengue fever. The best method of protection is to avoid mosquito bites and to reduce the mosquito population. When in a high-risk area, you should:
  • Avoid heavily populated residential areas
  • Use mosquito repellent indoors and outdoors
  • Wear long-sleeved shirts and pants tucked into socks
  • Use air conditioning instead of opening windows
  • Ensure that window and door screens are secure, and any holes are repaired
  • Use mosquito nets if sleeping areas are not screened
Reducing the mosquito population involves getting rid of mosquito breeding areas. These areas include any place that still water can collect, such as:
  • Birdbaths
  • Pet dishes
  • Empty planters
  • Flower pots
  • Cans
  • Any empty vessel
These areas should be checked, emptied, or changed regularly.

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